Arthropods play important roles in the life history of many macrofungi, including ectomycorrhizal and saprotrophic species that influence plant community ecology and ecosystem function. Fungivorous insects, which feed on fungal mycelia and spores, may affect fungal fitness through spore dispersal or damage to reproductive and vegetative structures. In turn, predaceous insects target fungal sporocarps to prey upon fungivores, creating complex communities of interacting species. Despite their ecological importance and capacity to serve as microcosms for understanding processes of community assembly, little is known about the factors shaping the composition of insect communities associated with macrofungi. Here, we used ecological network analysis and other methods to evaluate diversity, specificity, and variation in the structure of insect communities on macrofungal sporocarps (hosts) in mature hardwood forests of the central Appalachian Mountains, with a special focus on a numerically dominant order of macrofungus-associated insects (Coleoptera, beetles). Repeated field surveys over three growing seasons in four forest plots near Mountain Lake Biological Station, VA were used to assess the ways in which ecological network structure and community parameters differ as a function of insect trophic status (fungivore or predator) and host abundance, longevity, water content, and developmental stage.
Results/Conclusions
Over 24,500 adult beetles (ca. 119 species, 18 families) were collected and identified from 547 beetle-hosting sporocarps (ca. 65 species, 19 families). Analyses reveal a beetle community strongly dominated by Staphylinidae, with particular abundance and diversity in the subtribe Gyrophaenina (Staphylinidae: Aleocharinae). Community composition differed strongly with host developmental stage, showing marked turnover in species through sporocarp expansion and decay. On average, mature mushrooms tend to host communities consisting of specialist and generalist beetles, whereas communities in decaying mushrooms are dominated by more generalist taxa. Ecological network structure varied in characteristics such as connectance as a function of sporocarp age and water content, as well as beetle trophic status. This work reveals the variability of ecological networks as a function of developmental factors as well as functional traits of interacting species. Our study also represents one of the largest collections of insect-sporocarp association data to date and offers new insight into the structure and dynamics of a common and ecologically important fungal-insect interaction.